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Dec. 10, 1946.
J, A, PETRIE
2,412,533
DAMPING ARRANGEMENT FOR VEHICLE SUSPENSION SYSTEMS
Filed May 7, 1945
-
I’n Va 72 for,
‘115517165v A. Patna
W17, "fa-WW
A 1111:.
Patented Dec. 10, 1946
2,412,533
UNITED STATES PATENT OFFICE
2,412,533
DAMPING ARRANGEMENT FOR VEHICLE
SUSPENSION SYSTEMS’
James Alexander Petrie, Derby, England
Application May 7, 1945, Serial No. 592,396‘
In .Great Britain. May 22., 1944
5 Claims. (Cl. 188—88)
1
2
This invention is for improvements in, or re
lating to damping arrangements for vehicle sus
pension systems, and has for one of its objects to
the vehicle is travelling. Preferably the said
unloading means are responsive to movements of
enable a vehicle to ride over varying road sur
The said closing load may be applied by a
spring through a controlling piston which is ex
faces more smoothly than is possible with either
a non-adjustable or manually adjustable damp
ing system. As aircraft travel along the ground
in taking-off and landing, the term “vehicle” is
to be interpreted as including aircraft.
the vehicle axles.
v
posed to unloading pressure from damping ?uid
pumped against it past a, non-return valve by the
reciprocation of the said main piston, and con
veniently the said non-return valve controls a
Hydraulic shock absorbers for vehicle suspen 10 passage through the body of the damping valve.
There may alsobe combined with the said con
sion systems have been proposed in which the
movement of a damping piston (which is coupled
trolling piston an inertia-controlled spill valve
which is responsive to major vehicle shocks
to a part of the vehicle which moves under shock
caused by travel over major irregularities and is .
relatively to another part of the vehicle to which
adapted to relieve the said unloading pressure
latter the piston cylinder is connected) is used
from the controlling piston. Thus the shock ab
to vary the cross-sectional area of a passage
sorber is made self -adjusting, automatically free
through which the damping ?uid is forced, in
such manner that for light shocks causing little
ing itself to allow the road Wheels to follow minor
irregularities in the road, but by the operation of
displacement of the piston the intensity of the
the inertia-controlled spill valve becoming effec
damping effect is subjected to little, if any,
tive with increasing intensity should the chassis
change, whereas for heavier shocks causing
greater displacement of the piston the intensity
begin to bounce or pitch on its springs, until
such bouncing or pitching is damped out.
of the damping effect is correspondingly in
For a more complete understanding of the in
creased.
Double-acting hydraulic‘ shock absorbers for >iv 'al vention, there will now be described, by Way of
vehicles have also been proposed in which there
example only and with reference to the accom
i
are two aligned cylinders in which opposed pis
tons are reciprocated by a rock arm. As the pis
tons move, they cause damping liquid to pass
from the one cylinder to the other through a
passage which has a constriction somewhere in
it. Leakage from the cylinders is automatically
made up from a recuperator chamber through
valve-controlled passages.
According to the primary feature of the pres
ent invention there is provided a vehicle shock
absorber in which ?uid friction is employed for
damping, comprising the combination of a main
cylinder the ends of which are connected by a
conduit for the damping ?uid, a main piston re
panying drawing, one construction of shock ab
sorber according to the invention. It is to be
understood, however, that the invention is not
restricted to the precise constructional details set
forth.
The single ?gure is more or less diagrammatic
and is mainly in section.
The double-acting shock absorber shown in the
drawing comprises two aligned main cylinders
t9 and H in which opposed main pistons l2 and
!3 are reciprocated by a rock arm l4. As the
pistons l2 and i3 move, they cause oil or like
damping ?uid to pass from the cylinder ID to
the cylinder H or vice versa through a, conduit
ciprocable in said cylinder to force the damping
?uid through said conduit, a damping valve con
trolling the rate of flow of the ?uid through said
l5 controlled by a damping valve 18. The space
automatically controlled in such a manner that
a variable closing pressure is applied to it ac
and moves in a cylinder 23 having a port 24. The
damping valve L8 has a port 25 in it which can be
cording to the condition of the surface over which
closed by a spring-pressed non-return ‘valve 26.
in the shock absorber casing above and around
the cylinders Iii and H constitutes a recuperator
conduit, means for applying a closing load to said
chamber which is automatically drawn upon
damping valve, means for progressively unload 45 through valves 15 and I"!v to prevent the forma
ing the said valve down to a predetermined de
tion of air gaps in the cylinders l0 and H ‘and
gree and means responsive to major vehicle
conduit £5.
The damping valve I8 is urged towards closing
shocks caused by travel over major irregularities
position by a spring 1.9. and a spring 20-, therfor
for progressively restoring said closing load to an
appropriate degree. Thus it will be seen that 50 reel‘ of which, is enclosed in a ?anged shell 2|.
The spring 26 acts against a controlling piston
the movement of the damping ?uid by the main
22 which bears against the flange on the shell 2!
piston is constricted by a damping valve which is
2,412,533
3
4
One end of the damping valve [8 is exposed to
the pressure in the cylinder II and an annular
shoulder on the valve is exposed to the pressure
in the conduit 1-5 and thus to the pressure in the
cylinder l0.
Above the cylinder 23 is another cylinder 21
is in its weakest setting, applying the minimum
load to the damping valve IS.
The non-return valve 26 is opened only by pres
sure in the main cylinder H, which is effective
on upward movement of the vehicle axle. It is,
however, not so much provided to be relief valve
which communicates by a passage 28 with the
for the main cylinder II, as to be a non-return
aforesaid recuperator chamber. The cylinder 21
valve for the cylinder 23. Oil from the main
cylinder It] has ?rst to pass into the cylinder
has a central stem 29 with a passage 30 in it
connecting the interiors of the cylinders 23 and v10 ll before it can pass the non-return valve 26.
This arrangement was chosen because a smaller
21. The stem 29 serves to guide a weight 3|
which is screwed on to the upper end of a spill
valve 32 and constitutes an inertia member. A
damping force is required on the upward motion
spring 33 opposes the weight 3| and co-operates
with it to tend to maintain the valve 32 in po
sition to close the passage 30, but excessive jolt
ing or bouncing of the vehicle will cause the in
ertia-controlled spill valve 32 to open the said
turn valve 26 does, however, incidentally serve
passage.
of the axle than on the rebound.
The non-re
as a relief valve for upward ame movements.
The shock absorber resistance may always be
varying while the car is in motion, being a func
tion of axle movement tending to unload and
chassis movement tending to load it.
The general “ride” characteristics of the ve
hicle are determined initially by the rating of the
spring 33 carrying the inertia member 3|, a soft
applying the maximum load to the damping valve
spring being used for “hard” riding and vice
I8. When the vehicle is in motion any upward
versa. The whole is kept immersed in oil as
movement of the axle pumps oil past the non
shown to provide a constant degree of damping
return valve 26 causing the controlling piston
for this member by oil viscosity. Changes in the
22 to be displaced to the right against the spring
oil viscosity, due to temperature changes or other
20. This unloads the damping valve [8 to what
may be termed the “soft-riding” position by re
causes, are compensated. The less viscous the
oil is, the greater is the tendency to leakage from
lieving the spring pressure on the damping valve
l8. There is a- slight back oil pressure on the 30 the cylinder 23 and the resistance to movement
of the valve 32 offered by the oil is reduced. A
valve I8 when this occurs, but it is small in com
tendency to increase the load on the damping
parison with the reduction in spring load. The
valve results, thus maintaining the shock ab
controlling piston 22 can be displaced until the
When the vehicle is at rest the two springs l9 20
- and 20 in the cylinder 23 are in equilibruim and
port 24 is uncovered where it remains, passing
excess oil back to the recuperator chamber. This
is the position of “maximum softness” of damp
ing. Thus axle movements alone as distinct from
chassis movements progressively unload the
damping valve I8 down to a predetermined de
gree.
When the axle movements are violent enough
or of such a frequency as to build up appreciable
disturbances in the chassis. the spill valve 32,
sorption at the desired degree. Furthermore, the
constant circulation of the oil will help to keep
the shock absorber cool.
From the foregoing it will be seen that the self
adjusting shock absorber according to the pres
ent invention improves the comfort and safety
of a vehicle by minimising bouncing and pitching
tendencies of the chassis, and that the damping
force increases in proportion to the disturbances.
The sensitivity to chassis movement is better
than with previously proposed inertia-controlled
controlled by the inertia of the small spring
mounted weight 3!, is opened, by the relative 45 systems, because the inertia member in the pres
ent invention governs the damping valve through,
movement between the chassis and the weight,
what may be regarded as a low-pressure relay,
which tends to remain static. This discharges
and can therefore be small with a small ampli
oil from the cylinder 23 through the passage 30
tude of movement. This relay system protects
back to the recuperator chamber, thereby allow
ing the spring-pressure to build up again on the 50 the damping valve from erratic and non-synchro
nous movements of the inertia member and pro
damping valve 18.
motes smooth working of the shock absorber.
The inertia-controlled spill valve 32 is so de
The shock absorber is entirely self-contained and
signed that above a predetermined disturbance
free from extraneous manual and other forms
of the chassis it can spill oil faster than the non
return valve ‘26 can supply it, in which case the 55 of voluntary control during travel, with their
complication and distraction to the driver. On
maximum spring load is applied to the damping
good roads the shock absorber is normally kept
valve l8; hence maximum damping becomes ef
in the “soft” condition by slight pumping action,
fective. An additional adjustment is provided at
thereby permitting the axles to follow unex~
34 for the springs I29 and 20, to control the max
60 pected irregularities with the minimum of inter
imum resistance of the damping valve l8.
ference to the chassis. Upward movement of the
Oil passed from the main cylinder ll past the
axle always tends to unload the damping valve.
valve 26 is made up by oil drawn from the re
Finally
it may be mentioned that there is no dan
cuperator chamber via the valve H. The valve
l5 attends only to leakage from the main cylin 65 ger of relay oil ?ooding the shock absorber, as
there is with certain previously proposed pump
der ID. The valve ll must be capable of pass
operated systems external to the shock absorber.
ing somewhat more oil than can be passed by
It is to be understood that the invention is not
the valve 26, plus leakage.
restricted to the precise constructional details
The shock absorber can be maintained in the
set forth.
“soft” condition because oil pumped past the 70
I claim:
non-return valve 26 cannot escape from the cyl
1. A vehicle shock absorber in which ?uid- fric
inder 23 until the controlling piston 22 uncovers
tion is employed for damping, comprising the com
the port 24 by moving to the right, providing, of
bination of a main cylinder the ends of which
course, that the inertia-controlled spill valve 32
are connected by a conduit for the damping ?uid,
is not disturbed. In this condition the spring i9 75 a main piston reciprocable in said cylinder to
2,412,583
5
6
tion is employed for damping, comprising the
force the damping fluid through said conduit, a
damping valve controlling the rate of ?ow of
the ?uid through said conduit, means for pro
gressively unloading the said valve down to a
predetermined degree, and means responsive to
vehicle shocks caused by travel of the vehicle for
progressively restoring the closing load on the
valve.
2. A vehicle shock absorber in which ?uid fric
tion is employed for damping, comprising the
combination of a main cylinder the ends of which
are connected by a conduit for the damping ?uid,
a main piston reciprocable in said cylinder to
force the damping ?uid through said conduit, a
damping valve controlling the rate of ?ow of the
?uid through said conduit,'means responsive to
movements of the vehicle axles for progressively
unloading the said valve down to a predetermined
degree, and means responsive to vehicle shocks
caused by travel of the vehicle for progressively
restoring the closing load on the valve.
3. A vehicle shock absorber in which ?uid fric
tion is employed for damping, comprising the
combination of a main cylinder the ends of which
are conected by a conduit for the damping ?uid,
a main piston reciprocable in said cylinder to
force the damping ?uid through said conduit, a
damping valve controlling the rate of ?ow of the
?uid through said conduit, a controlling piston
and a spring co-operating therewith for applying '
a closing load to said damping valve, a non-re
turn valve controlling a passage through which,
past the non-return valve, damping ?uid is
pumped against the controlling piston by the re~
ciprocation of the said main piston to progres
sively unload the damping valve down to a pre
valve which is responsive to major vehicle shocks
caused by travel of the vehicle and is adapted to
relieve the said unloading pressure from the con
determined degree, and means responsive to ve
hicle shocks caused by travel of the vehicle for
progressively restoring said closing load on the
valve.
4. A vehicle shock absorber in which ?uid fric
combination of a main cylinder the ends of which
are connected by a conduit for the damping fluid,
a main piston reciprocable in said cylinder to
force the damp-ing ?uid through said conduit, a
damping valve controlling the rate of ?ow of the
?uid through said conduit, a controlling piston
and a spring co-operating therewith for apply
ing a closing load to said damping valve, a non
retum valve controlling a passage through the
body of the damping valve through which pas
sage, past the non-return valve, damping ?uid is
pumped against the controlling piston by the re
ciprocation of the said main piston to progres
sively unload the damping valve down to a pre
determined degree, and means responsive to ve
hicle shocks caused by travel of the vehicle for
progressively restoring said closing load on the
valve.
5. A vehicle shock absorber in which ?uid fric
tion is employed for damping, comprising the
combination of a main cylinder the ends of which
are connected by a conduit for the damping ?uid,
a main piston reciprocable in said cylinder to
force the damping ?uid through said conduit, a
damping valve controlling the rate of ?ow of the
?uid through said conduit, a controlling piston
and a spring co-operating therewith for applying
a clOSiIlg load to said damping valve, a non-re
turn valve controlling a passage through which,
past the non-return valve, damping ?uid is
pumped against the controlling piston by the re
ciprocation of the said main piston to progres
sively unload the damping valve down to a pre
determined degree, and an inertia-controlled spill
trolling piston.
40
JAMIES ALEXANDER. PETRIE.
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